HISTORY AND DEVELOPMENT
Arthur C Clarke created a book about the first-ever ramjet design. It is the first fictional example of a rocket-powered space flight.
The first patent of a subsonic ramjet cycle device, an ejector ramjet, was issued to Lake in 1909. Lorin published the first treatise on subsonic ramjets in 1913 but did not address high subsonic or supersonic flight.
French scientist Rene Lorin created a prototype of a ramjet, but his project failed because of a limited supply of materials. He designed the ramjet to have a piston internal combustion engine with extra exhaust nozzles.
Albert Fono, an inventor in Hungary, created ramjet-like projectile propulsion to allow heavy shells to be fired from lightweight devices.
Carter in Great Britain patented the first practical ramjet-like device for enhancing the range of artillery shells in 1926. Carter’s designs showed considerable insight for the time and employed a normal shock inlet with either a conical nose/annular duct or central cylindrical duct.
- The first recognizable conical-nosedLFRJ patent was given to Fono in Hungary in 1928. These designs included convergent-divergent inlet diffusers, fuel injectors, flame holders, combustors, and convergent-divergent nozzles. Although these systems were designed for supersonic, high-altitude aircraft flight, they did not advance beyond the design stage.
The Boris Stechkin presented in the Sovient Union a supersonic ramjet engine. His goal is to simulate supersonic flight and to give way to the development of advanced propulsion technologies.
- The first engine (GIRD-04), was designed by I.A. Merkulov and tested in April 1933. To simulate supersonic flight, it was fed by air compressed to 20,000 kilopascals (200 atm), and was fueled with hydrogen. The GIRD-08 phosphorus-fueled ramjet was tested by firing it from an artillery cannon. These shells may have been the first jet-powered projectiles to break the speed of sound.
Mstislav Keldysh designed a long-range antipodal bomber in 1947, modeled after the Sänger-Bredt bomber but driven by ramjet rather than rockets. Burya, a Mach 3 ramjet-powered cruise missile, was first developed by NPO Lavochkin and the Keldysh Institute in 1954.
DFL’s Eugen Sänger presented a ramjet engine with a high combustion chamber temperature in 1941. He built unusually enormous ramjet pipes with diameters of 500 millimeters and 1,000 millimeters and tested them on lorries and a special test rig on a Dornier Do 17Z at rates of up to 200 meters per second. Later, when petrol became limited in Germany due to the war, tests were carried out using blocks of pressed coal dust as fuel, but these were unsuccessful due to poor burning.
The United States Navy created a series of air-to-air missiles known as “Gorgon” that used various propulsion methods, including ramjet propulsion on the Gorgon IV, which was tested at Naval Air Station Point Mugu in 1948 and 1949. The ramjet engine was created by the Marquardt Aircraft Company and designed by the University of Southern California.
Blue Envoy, a project that was designed to provide the country with a long-range ramjet-powered air defense system against bombers, was eventually abandoned. It was superseded by the Bloodhound, a much shorter-range ramjet missile weapon. The system was created as a backup in case invaders managed to get past the defending fleet of English Electric Lightning fighters.
Waltrup5 provided a very thorough review of international airbreathing engine development from the beginning years to 1987, with an emphasis on the development of supersonic combustion ramjet engines.
The ramjet received expanded international development attention beginning in the 1980s, which continues today. During the 1980s France developed the operational Air-So Moyenne Portee-Ameliore (ASMP) and flight-tested Missile Probatoire Stato Rustique. The United States invested effort in supersonic low-altitude target (SLAT) and VFDR.
During the 1990s, France continued its long history of development activity in ramjets with activity on MARS, MPSR/Rustique, Anti-Naivre Futur/AntiNavire Nouvelle Generation ANF/ANNG, Vesta, and the next generation ASMP-A. The People’s Republic of China began the development of a long-range anti-ship variant(C-301) of its C-101 and the more advanced Hsiung Feng.
South Africa began the development of a long-range air-to-air missile (LRAAM). Russia continued to demonstrate its understanding of this technology by beginning the development of AA-X-12 and SS-N-26. Israel entered the ramjet community by beginning the development of a ramjet-powered version of Gabriel for an extended range. Germany began the development of an anti-radiation missile ARMINGER. India began the development of the PJ-10/Brahmos, a derivative of the Russian SS-N-26.
The 2000s have seen the ramjet development activity continue and expand yet further in the United States supersonic sea-skimming target (SSST), generic supersonic cruise missile (GSSCM), and high-speed antiradiation demonstration (HSAD), The United Kingdom beyond visual range air-to-air missile (BVRAAM/Meteor), France (MICA/RJ), and elsewhere. These and other international development programs are reviewed in further detail later in this paper as a means of better understanding the evolution of ramjet technology.
President Vladimir Putin declared on March 1, 2018, that Russia had constructed a prototype of a nuclear-powered ramjet cruise missile capable of long-range flight.
The diffuser is the primary component of a ramjet, and it utilizes the ramjet’s forward momentum to increase the pressure of its working fluid (air), which is required for fuel combustion. It is then amplified to supersonic speeds after passing through a nozzle. The ramjet generates forward thrust as a result of this acceleration.
- Is it the component of the ramjet which converts the air’s high velocity into high static pressure needed for burning. High combustion pressures reduce the amount of wasted thermal energy in the exhaust gases.
- Its primary purpose is to increase the air temperature by burning fuel. This occurs with only a marginal loss of pressure. The air velocity entering the combustor must be low enough for constant combustion to take place in flame holders’ insulated zones.
- As it accelerates exhaust flow to produce thrust, the propelling nozzle is a crucial component of the ramjet design. Subsonic ramjets is using a nozzle to increase exhaust flow. A convergent–divergent nozzle is typically required for supersonic flight.
The operation of a ramjet engine works under the principle of air being taken in by the diffuser and then compressed into two stages. It draws in air with the craft’s forward speed and compresses the air for combustion through a specially formed intake passage. Combustion is self-sustaining when fuel is injected into the engine and ignited. Forward force is generated by the backward surge of hot exhaust gasses, just like in other jet engines.
The air is forced to change its route by the weight of the approaching engine, which causes external compression. In the diverging part of the ramjet diffuser, more compression is achieved. In the diffuser, fuel is injected and combined with air. The flame holder creates a low-velocity zone that is conducive to flame propagation, and the fuel-air combination recirculates within this shielded area, igniting the fresh charge as it passes the flame holder’s edge. The temperature and volume of the burning gasses increase as they pass through the combustion chamber. Because the volume of air grows, it must accelerate to avoid colliding with the fresh charge approaching from behind, resulting in an increase in velocity as the air is squeezed out of the exit nozzle. The engine’s thrust is related to the rate of change in velocity.
Ramjets perform best at speeds of Mach 2 or greater (twice the speed of sound). Since ramjets have no static thrust, they need a way to launch them at high velocities. Because of this they are found almost exclusively in missiles, where they are boosted to operating speeds by a rocket engine, or by being attached to another aircraft (typically a fighter).
A number of contemporary missile concepts use ramjet engines to obtain higher fuel efficiency (and consequently, longer range) at supersonic speeds than a rocket-driven approach. The MBDA Meteor air-to-air missile and the Russian-Indian BrahMos supersonic cruise missile are two examples.
The combined cycle engine is a version of the pure ramjet engine that is designed to overcome the constraints of the pure ramjet engine. A good illustration of this is the SABRE engine, which employs a precooler, which is then followed by the ramjet and turbine equipment.
An experimental implementation of this notion is the ATREX engine, which has been created by the Japanese government. It operates on liquid hydrogen fuel in a single-fan configuration that is somewhat unusual. Liquid hydrogen fuel is fed via an air intake heat exchanger, which heats the liquid hydrogen fuel while simultaneously chilling the incoming air. This cooling of the entering air is necessary in order to achieve a fair level of efficiency in the system.
Following the combustion part, the hydrogen passes through a second heat exchanger position, where the hot exhaust is used to further heat the hydrogen, transforming it into a very high pressure gas. This gas is then forced through the fan’s tips, where it provides driving power to the fan while it is operating at subsonic speeds. It is burned in the combustion chamber once it has been mixed with the air.
McCutcheon, K. D. (2020, September 1). WWII Lorin Ramjet Experiments. Aircraft Engine Historical Society. Retrieved April 11, 2022, from https://www.enginehistory.org/Rockets/LorinRamjet/LorinRamjet.shtml
Popular Mechanics article that covers the USAF first experiment with ramjets. (n.d.). Google books: Riding the Ramjet. https://books.google.com.ph/books?id=YyQDAAAAMBAJ&pg=PA130&dq=1949+Popular+Science+%22Popular+Science%22+first+flat+top+ever+designed&hl=en&ei=32DGTNGkGcL9nAeD9JChAQ&sa=X&oi=book_result&ct=result&redir_esc=y#v=onepage&q&f=true
Ramjet Propulsion11.05.03. (2009, April 10). NASA.
22Waltrup, P. J., White, M. E., Zarlingo, F., and Gravlin, E. S., “History of U.S. Navy Ramjet, Scramjet, and Mixed-Cycle Propulsion Development,” AIAA Paper 96-3152,July 1996.
24Kuentzmann, P., and Falempin, F., “Ramjet, Scramjet and PDE—An Introduction,” Encyclopedia of Physical Science and Technology, 3rd ed., Academic Press, Vol. 13, 2002.
8McClinton, C. R., Andrews, E. H., and Hunt, J. L., “Engine Development for Space Access: Past, Present and Future,” International Symposium on Air Breathing Engines, ISABE Paper 2001-1074,Jan. 2001.
BrainKart.com. (n.d.). Gas Dynamics and Jet Propulsion: The Ramjet Engine. BrainKart. https://www.brainkart.com/article/The-Ramjet-Engine_5099/